1. Field of the Invention
The present invention relates to a semiconductor device and a method of forming the same, and more particularly, to a semiconductor device having a contact and a method of forming the same.
2. Description of the Related Art
As the integration density of semiconductor devices increases, the area of cells formed in semiconductor devices and the critical dimension CD of bit lines decrease considerably. Also, contact holes connecting bit lines and lower conductive layers are refined. As a result, the ratio of the depth to the diameter of a contact hole, i.e., the aspect ratio, is increased, and the contact hole needs a plug material having excellent gap-filling characteristics.
FIGS. 1 through 4 are cross-sectional views describing a semiconductor device having a general contact and the steps of a method of forming the same. Referring to FIG. 1, an interlayer dielectric layer 14 is formed on a semiconductor substrate 10 having a lower conductive layer 12. A contact hole 16 is formed by selectively etching a portion of the interlayer dielectric layer 14 to expose the lower conductive layer 12.
With reference to FIG. 2, an ohmic layer 18 is formed by depositing a conductive material on the exposed lower conductive layer 12. A first barrier layer 20 is formed on the entire surface of the contact hole 16 and the interlayer dielectric layer 14 by a blanket method.
Referring to FIG. 3, a conductive layer 22 is formed on the entire surface of the semiconductor substrate 10, on which the first barrier layer 20 is formed, to form a contact plug. The conductive layer 22 is formed of a material having excellent gap-filling capability and step coverage for the contact hole 16.
With reference to FIG. 4, the first barrier layer 20 and the conductive layer 22 are removed and planarized to expose the surface of the interlayer dielectric layer 14 by using chemical mechanical polishing and an etch back process. A second barrier layer 24 and an upper conductive layer pattern 26 are sequentially formed on a contact plug 22xe2x80x2 that is formed by a planarization process.
In general, tungsten W is used as the material for the contact plug 22xe2x80x2 because tungsten has low contact resistance, excellent adhesion, and fine step coverage to the ohmic layer 18. However, fluorine F contained in a tungsten plug moves to the ohmic layer 18 when thermally treated and thus, nonconductive Tixe2x80x94F compound is formed. In order to solve this problem, titanium nitride TiN has recently been used as the contact plug 22xe2x80x2.
Residual stress is generated in a process of forming the conductive layer 22 for forming a contact plug. For example, titanium nitride TiN is generally deposited to a thickness of 1500 xc3x85 or more to fill the contact hole 16 fully. In this case, the titanium nitride TiN layer is cracked due to residual stress while stabilizing the titanium nitride TiN layer after the deposition. Also, the crack in the titanium nitride TiN layer causes a crack in the interlayer dielectric layer 14. The probability of a crack occurring increases with an increase in the aspect ratio of the contact hole 16.
To solve the above problems, it is a first object of the present invention to provide a method of forming a contact which can prevent damage to an interlayer dielectric layer due to residual stress generated on a conductive layer use in forming a contact plug.
It is a second object of the present invention to provide a semiconductor device having a contact which can prevent damage to an interlayer dielectric layer due to residual stress generated on a conductive layer used in forming a contact plug.
Accordingly, in accordance with a first aspect of the invention, there is provided a method of forming a contact using a crack-protecting layer. An interlayer dielectric layer is formed on a semiconductor substrate on which a lower conductive layer is formed. A crack-protecting layer is formed of a dielectric layer on the interlayer dielectric layer. A contact hole is formed by etching the crack-protecting layer and the interlayer dielectric layer to expose the lower conductive layer. A conductive layer is formed to form a contact plug which fills the contact hole and covers the semiconductor substrate. The conductive layer is planarized.
The crack-protecting layer relieves or absorbs residual stress transferred from the conductive layer to the interlayer dielectric layer. The crack-protecting layer may be formed by a chemical vapor deposition (CVD) method or a spin-on glass (SOG) method.
The crack-protecting layer formed by the CVD method can be a single layer formed of one of SiOF, SiN, SiO2, SiOC, and TEOS, or is a compound layer containing at least one of SiOF, SiN, SiO2, SiOC, and TEOS. The crack-protecting layer formed by the SOG method can be a single layer containing one of a material having an inorganic silicide source and a material having an organic siloxane source, or can be a compound layer containing at least one of a material having an inorganic silicide source and a material having an organic siloxane source. The interlayer dielectric layer is formed of a material which is easily cracked due to residual stress transferred from the conductive layer.
In accordance with a second aspect of the invention, there is provided a semiconductor device in which a contact is formed using a crack-protecting layer. The semiconductor device includes a semiconductor substrate having a lower conductive layer; an interlayer dielectric layer formed on the semiconductor substrate and having a contact hole exposing the lower conductive layer; a crack-protecting layer formed on the interlayer dielectric layer; a contact plug for filling the contact hole; and an upper conductive layer formed on the contact plug.
The crack-protecting layer can be a single layer formed of one of SiOF, SiN, SiON, SiO2, SiOC, and TEOS, or a compound layer containing at least one of SiOF, SiN, SiON, SiO2, SiOC, and TEOS. The crack-protecting layer has a thickness of 100-1500 xc3x85.
When a contact plug is formed, a crack-protecting layer relieving or absorbing residual stress is formed. As a result, a contact is formed without damage to an interlayer dielectric layer.